The Horizon program I blogged about yesterday explored some cutting edge ideas about what really makes us fat – the big surprise was that a major player is one of the genes that controls insulin. It also tested a radical new idea that fasting could be an effective way of turning off that gene. Both topics are covered in some detail in my Healthy Ageing book written with nutritionist Patrick Holford. So here are a few extracts if you want to know more.
“Of course the idea of dealing with obesity by eating less is hardly new. It’s the central plank of most weight loss programs. So what is the difference between a regular calorie-controlled diet and calorie restriction (CR) which is the key to turning down that insulin gene?
Calorie-counting diets last for only a few weeks, or months at the most, and they nearly always come up against the problem that your body’s metabolism slows down to compensate. Once you stop the diet, the pounds rapidly pile back on. Full time CR, however, is something that you do for life, eating about 25% less than a normal adult needs. It can make dramatic and lasting changes to your metabolism – blood pressure, blood sugar, weight all improve. But you need the willpower of an Olympic athlete to put up with feeling cold and hungry for ever.
Gain without the pain – CR ‘mimetics’
One way round this is to find compounds – known as CR mimetics – that have a similar effect and could be turned into a pill. And here you venture into specialised and controversial anti-ageing territory. The best-known one is resveratrol, an anti-oxidant found in grape skins and so a possible explanation for the health benefits of red wine. Some studies have found it increases animals’ life spans; it is also anti-inflammatory and lowers blood sugar.
Other possible pills include carnosine (an antioxidant made in the body, especially in the muscles), L-carnitine, which carries fat into mitochondria (the energy generating power plants found in every cell) and two more antioxidants: lipoic acid, and CoQ10. However lots more research is needed to prove their effectiveness and safety.”
So the scientific interest in CR is not because it is a realistic way of allowing you to live a longer and healthier life but because it shows that it is possible. So to make best use of it you have to know how it works and this is where the Methuselah Worm comes in.
The Methuselah Worm
“Several years ago Professor Cynthia Kenyon, a top geneticist at the University of California, San Francisco, wondered why CR had such a dramatic health benefits. Assuming that the drop in food intake must be having some effect on the behaviour of genes, she began a series of experiments, cutting back on the calorie intake of tiny roundworms just a millimetre long, known as Caenorhabditis elegans, which are the genetics researcher’s ‘lab rat’.
She found that one gene in particular was turned off by the CR diet. To her big surprise, it was one that normally made more insulin available. Even more of a surprise was the finding that turning the insulin gene off, turned on another gene that controlled a cascade of extensive cell-repair processes. By tinkering with these genes she was able to breed some worms that lived for twice their normal 20-day lifespan. Recently, with more sophisticated techniques, she’s been able to genetically engineer a strain of C. elegans that lives healthily and actively for an astonishing 144 days. The human equivalent of 450 years!”
Cutting your risk of cancer and Alzheimer’s
So what you’ve got here is a direct genetic link between the way you eat (and maybe what you eat) and the benefits of low levels of the hormones insulin and insulin-like growth factor (IGF-1). In fact, evidence is growing that your blood levels of glucose and insulin are strong predictors not just of your diabetes risk but also of a shorter life span, as well as raising your risk of cancer and possibly Alzheimer’s.
All of which points to another way of getting the health gains of CR without the pain – follow what’s called a low-GL (glycemic load) diet, which essentially means one that has very little of the refined carbohydrates that are rapidly turned to glucose in the blood. Full details of how to do this can be found in the “10 Secrets of Healthy Ageing”.
“As a result of her findings Professor Kenyon has been keeping her carbohydrate intake really low. The turning point for her was the discovery that giving her Methuselah worms just a drop of glucose rapidly made them wrinkly and dead. High blood sugar, which triggers insulin, means that IGF-1 gene never gets turned down, so the gene that controls the repair process (dubbed “Sweet Sixteen”) never gets activated.
‘Ever since these findings I’ve cut out all starch such as potatoes, noodles, rice, bread and pasta,’ says Professor Kenyon. ‘Instead I have salads but no sweet dressing, lots of olive oil and nuts, tons of green vegetables along with cheese, chicken and eggs.’”
Coming shortly: Alternate Day Dieting. The ultimate way to get the gain of CR without the pain.
Body of Evidence 
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